Handheld vacuum cleaners are popular with users due to their light weight and inherent portability, as well as the lack of power cords, which makes such vacuum cleaners particularly convenient for spot cleaning tasks as well as for cleaning larger areas. The cleaning efficiency of handheld vacuum cleaners is improving and it is known to equip a handheld vacuum cleaner with a cyclonic separating apparatus to separate the dirt and dust from the incoming flow of dirt laden air. One such example is disclosed in EP2040599B, which incorporates a first cyclonic separating stage in the form of a relatively large cylindrical cyclone chamber and a second cyclonic separating stage in the form of a plurality of smaller cyclones fluidly downstream from and arranged in a ring-like configuration around the first cyclonic separating stage. In such an arrangement, the first cyclonic separating stage works to separate relatively large debris from the airflow, whilst the second cyclonic separating stage filters relatively fine dirt and dust from the airflow by virtue of the increased separation efficiency of the smaller cyclones.
Increasing the number of parallel cyclones generally increases the separation efficiency of the apparatus for a given air flow resistance. However, the provision of an increasing number of smaller dimension cyclones, typically arranged in a ring, has the knock on effect of increasing the diameter and, more broadly, the overall size of the separating apparatus. Although steps can be taken to minimize the dimensions of the cyclones in the second stage, the extent of the size reduction is limited since simply reducing the size of the cyclones brings with it other problems, for example high air flow resistance and cyclone blocking. Furthermore, the separating apparatus must also be provided with outlet ducting for fluid to exit the separating apparatus in such a way as to enable the separating apparatus to be packaged in a compact manner so as to be more suited to use on a portable machine. It is with these issues in mind that the invention has been devised.